In PCT application PCT/GB96/03060 (published as WO 97/21630) there is disclosed desalination apparatus which includes a series of spirally wound reverse osmosis membranes in a cylindrical outer casing. The casing has a cap at each end. The caps close the ends of the casing. The raw water inlet, the permeate outlet and the brine outlet pass through the caps.
Between the cap through which the raw water inlet passes and the adjacent end of the first of the membranes in the casing there is a flow distributor plate. The plate has a multitude of bores passing through it and streams of raw water flow through these bores. The water streams impinge on the end of the first membrane and the water flows into the salt retention passages.
The flow distributor plate of the desalinator disclosed in WO 97/21630 has a flat front face and the bores in the plate can have their axes skew to the flat front face of the plate.
The present invention provides an improved flow distributor plate for reverse osmosis desalination apparatus.